Absolute normalisation of the LHC measurements with a precision of O(1%) is
desirable but beyond the reach of the present LHC detectors. This series of
papers proposes and evaluates a measurement method capable to achieve such a
precision target. In our earlier paper we have selected the phase-space region
where the lepton pair production cross section in pp collisions at the LHC can
be controlled with < 1 % precision and is large enough to reach a comparable
statistical accuracy of the absolute luminosity measurement on the day-by-day
basis. In the present one the performance requirements for a dedicated
detector, indispensable to efficiently select events in the proposed
phase-space region, are discussed.Comment: 26 pages, 13 figure
